1. Field of the Invention
The present invention relates to the process of etching thin films in the manufacturing of semiconductor devices. More particularly, the present invention relates to a window that allows the end point of an etching process to be determined and to an etching device comprising the same.
2. Description of the Related Art
Currently, semiconductor devices are being developed at a rapid pace due to the widespread use of computers for processing various types of information. Semiconductor devices must operate at high speeds and have the capacity to store a large amount of information. The current art is thus focused on developing and realizing memory devices having a high degree of integration, response speed, and reliability. In this respect, the manufacturing of semiconductor memory devices must include highly precise process techniques, such as thin film forming and etching techniques, if the devices are to be highly integrated.
The etching technique removes predetermined portions of films formed on a semiconductor substrate to produce a desired pattern. These days, the typical design rule of a semiconductor device manufacturing process is less than 0.15 xcexcm. Accordingly, dry etching devices using plasma are mainly used for etching films on a semiconductor substrate.
Although plasma etching devices differ slightly from one another depending on the method in which they form the plasma, the devices all include a process chamber having a chuck for supporting a substrate, and a plasma forming section. Still further, various elements are provided in the process chamber for ensuring that the film formed on the substrate is etched a precise amount. These elements include an end point detection window for transmitting light generated during the etching process and a detector for sensing the wavelength of the light transmitted through the end point detection window.
An example of a method of and apparatus for detecting the end point of an etching process by sensing the wavelength of the light irradiated during the etching process is disclosed in U.S. Pat. No. 5,288,367 issued to Angell et al.
Angell et al. disclose an end point detection window attached to a sidewall of a process chamber so as to allow the light in the process chamber to be transmitted out of the process chamber. In addition, the end point detection window is made of quartz for effectively transmitting the light.
The side of the end point detection window that faces the interior of the process chamber is referred to as the upper surface of the window, whereas the other side of the end point detection window is referred to as the lower surface. The upper surface of the end point detection window has a hole at the center thereof. The bottom of the hole is blocked at the lower surface of the end point detection window. Therefore, when etching the films, the radiated light passes through the hole formed in the end point detection window. However, plasma ions in the process chamber cannot be transferred to the detector because the bottom of the hole is blocked.
Nonetheless, the conventional end point detection window has several problems.
Firstly, the conventional end point detection window can be easily broken. The frequent replacing of a broken end point detection window adds significantly to the manufacturing cost of the semiconductor devices and requires much down time, thereby lowering the productivity of the manufacturing process.
In addition, the conventional end point detection window generates particles during the etching process. These particles may cause the etching process to fail. More specifically, part of the plasma generated during the etching process collides with the inner wall surface of the detection window that defines the hole therein. As the etching process is continuously performed, the inner wall surface is thus damaged over time.
Generally, the inner wall surface of the quartz end point detection window is processed so as to be smooth. As a result of this process, the inner wall surface has a great deal of grain boundaries. For this reason, portions of the inner wall surface are easily broken. The particles of the broken quartz drop onto films formed on a wafer, which are subject to the etching process. Such quartz particles have a silicon or oxygen component that prevents appointed areas of the films from being etched, thereby creating bridges between patterns.
FIG. 1 is a graph produced by an EDS (Energy Dispersive X-ray Spectrometer) showing a componential analysis of a bridge section of a patterned film. The patterned film was formed using an etching device having a conventional end point detection window. As shown in the graph, oxygen (A) and silicon (B) are detected in the bridge section. Because the inner wall of the process chamber is made of aluminum or an aluminum alloy, the silicon and oxygen are deemed to derive from particles separated from the quartz end point detection window.
An object of the present invention is to obviate the above problems of the prior art. Therefore, a first object of the present invention is to provide an end point detection window capable of reducing process failures in an etching process. Likewise, an object of the present invention is to provide an etching device which is not prone to creating process failures.
The end point detection window comprises a body of aluminum or an aluminum alloy attached to a side of the process chamber of the etching device, and a quartz cap coupled to the body. The body has a hole extending therethrough defining a route along which light generated during an etching process can pass. The quartz cap is coupled to a light outlet at the bottom of the hole in the body for allowing light passing through the hole to be transmitted out of the process chamber.
In addition to the process chamber, in which an etching process is carried out for patterning films formed on a substrate, and the end point detection window, the etching device includes a detecting section for detecting the wavelength of light transmitted through the end point detection window. The detection section may include an optical cable having one end connected to the quartz cap, a detector connected to the other end of the optical cable, and an optical filter disposed in the optical cable. The detector may comprise a spectrometer and a PMT (photomultiplier) tube.
The end point detection window of the present invention can withstand the bombardment of plasma ions produced during the etching process. That is, the aluminum or aluminum alloy body of the detection window is hardly abraded by the plasma ions. Therefore, process failures, such as the bridging of patterns formed by the etching process, are minimized.